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Increase buffer for nmap arguments when "--resume" a scan #1659

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@cnotin
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commented Jul 10, 2019

I have a complicated nmap scan with a long list of ports (used both for "-PS", SYN ping, and "-p", SYN port scan).
Here is what happens when I try to resume this scan (using the .nmap or .gnmap files):

nmap --resume myscan.nmap
Unable to parse supposed log file myscan.nmap. Perhaps the Nmap execution had not finished at least one host? In that case there is no use "resuming"
QUITTING!

I found that the issue is that the arguments string length is higher than 1024 which is currently not supported:

nmap/nmap.cc

Line 2339 in 23ee017

char nmap_arg_buffer[1024];

nmap/nmap.cc

Lines 2392 to 2393 in 23ee017

if (!q || ((unsigned int) (q - p) >= sizeof(nmap_arg_buffer) - 32))
fatal("Unable to parse supposed log file %s. Perhaps the Nmap execution had not finished at least one host? In that case there is no use \"resuming\"", fname);

I chose arbitrarily the new value of "1024*128" but it seems large enough while being a reasonable size (131ko). Also based on this, but it is not a definite answer:
https://serverfault.com/a/163390
With the patch I can confirm that my scan can properly resume.

As a side note, I think that the displayed error message has no relation with the issue here.

@nnposter

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commented Jul 14, 2019

There is a 4K limitation in arg_parse() so I assume that your specific scan had to fit into that. I have increased the resume buffer accordingly.

Thank you for contributing to nmap.

@nnposter nnposter self-assigned this Jul 14, 2019

@nnposter nnposter added bug Nmap labels Jul 14, 2019

@nmap-bot nmap-bot closed this in 4e6fef4 Jul 14, 2019

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